Power converters are essential for many modern electronic devices. Among other capabilities, a power converter can adjust voltage level downward (buck converter) or adjust voltage level upward (boost converter). A power converter may also convert from alternating current (AC) power to direct current (DC) power, or vice versa. Power converters are typically implemented using one or more switching devices, such as transistors, which are turned on and off to deliver or supply power to the output of the converter. Such a power converter may be incorporated into or used to implement a power supply—i.e., a switching mode power supply (SMPS).
In some applications, it is desirable for a SMPS to be capable of burst mode operation. This is common for battery-powered electronic devices (such as portable cellular telephones, laptop computers, etc.) that have a normal operating mode, in which the devices consume a relatively large amount of power, and a standby operating mode (e.g., a sleep mode), in which the devices consume relatively little power. In the normal operating mode, the switching device of the SMPS is switched on and off continuously at a predetermined frequency. In the standby operating mode, the switching device is switched on and off in bursts having a predetermined frequency. The electronic devices will automatically enter the standby operating mode when a user has not interacted with the device for a predetermined amount of time, thereby conserving battery power. The electronic devices will automatically exit the standby operating mode and enter the normal operating mode when a user interacts in some way with the device, for example, by pushing a control button, mouse, etc.
In other applications, however, such as audio power, modems, PABX, and other telecommunication, etc., burst mode operation is not desirable because it generates audible noise and high ripple voltage. Microcontrollers in modems are very sensitive to ripple voltage. Power supplies operating in burst mode operation can make these microcontrollers malfunction.
From the perspective of a manufacturer of power converter parts, it is undesirable to produce two different parts in which the only difference between the parts is the presence or absence of burst mode functionality. Also, from the perspective of a manufacturer of a variety electronic devices, it is desirable to be able to use the same part in many different kinds of products—e.g., television sets, DVD players, computers, handheld telephones, modems, PABX devices, etc. This simplifies ordering and inventory management.